Cranes for handling such as installing and dismantling of components of a wind turbine nacelle and cranes for handling and/or servicing outer components of the wind turbine are often provided as a stationary part or an intermediate part of the nacelle as such. The components of the nacelle may be any component. The major components of the nacelle are the generator, the gear box if such is provided and a transformer if such is provided. Possibly also a main shaft and bearings may be major components of the nacelle. The outer components of the wind turbine may be the blades, the hub, the nacelle itself and the tower.
Other solutions of cranes have been proposed, where the cranes do not form part of the nacelle as such, and where the cranes are intended for being attached to the wind turbine tower.
WO 2006/077358 discloses a self-advancing climbing device including two clamps, and a method of coupling such a clamp to, for example, a wind turbine tower. The clamp comprises at least one clamp member in the form of a friction pad adapted to grip the tower, and at least one flexible elongate element in the form of a tendon adapted to exert a force on the friction pad to urge the pad to grip the tower, whereby the pad and the tendon are adapted to exert a substantially uniform radial clamp load on the tower. The tendon and the pad form part of a rigid frame having a fixed size in relation to the circumferential size of the wind turbine tower.
WO 2004/092577 discloses a method of servicing the outer components of a wind turbine such as the wind turbine blades and the tower with a work platform. The method comprises the steps of positioning the work platform at the wind turbine tower and connecting the work platform to an upper part of the wind turbine with at least one cable. Furthermore the method comprises the steps of raising the work platform with the cable and cable winding means to a position of use, and holding the work platform to the side of the wind turbine tower with holding means. The invention also relates to a work platform for servicing the outer components of a wind turbine. The work platform is held in position of use by being suspended from the cables and is only intended for servicing outer components of the wind turbine, mainly for servicing the blades.
DE 196 43 515 discloses a mechanism with two or more parts with a foot and a head temporarily forming a unit with the wind turbine tower, to which the foot and head are detachably secured. The mechanism has two or more hydraulic rams, giving a climbing sequence. The jib of the mechanism is equipped with a rope, by which the sections of the tower are successively placed one above the other. After this, the nacelle with gearbox generator and rotor blades is installed, and descent takes place using the mechanism in the reverse climbing sequence. The climbing mechanism is either dependent on individualised gripping features being provided as at least an intermediate part of the wind turbine tower as such or the climbing mechanism comprises a rigid frame having a fixed size in relation to the circumferential size of the wind turbine tower.